Liquid Nitrogen

Nitrogen is the most common substance in Earth's _________crustoceansatmospheretrees. In the Earth's atmosphere, nitrogen is a gas. The particles of a gas move very quickly. They run around and bounce into everyone and everything. The hotter a gas is, the _________slowerfasterhottercolder the particles move.

When a gas is _________cooledwarmedheatedcompressed, its particles slow down. If a gas is cooled enough, it can change from a gas to a liquid. For nitrogen, this happens at a very _________strangewarmlowhigh temperature. If you want to change nitrogen from a gas to a liquid, you have to bring its temperature down to 77 Kelvin. That's 321 degrees below zero _________KelvinCelsiusCentigradeFahrenheit!

Liquid nitrogen looks like water, but it acts very differently. It disappears as soon as it touches the floor because it rapidly _________explodesboilsfreezesdries and changes back to a gas at room temperature. A flower dipped in liquid nitrogen will shatter because all of the water in the flower freezes instantly. An inflated _________flowersockpuppetballoon placed in liquid nitrogen will appear to slowly deflate. The air isn't leaving the balloon, though. It's just taking up less space because it's getting cold and its particles are moving slower. Once the balloon is removed from the liquid nitrogen, it warms back up and returns to normal.

Although experimenting with liquid nitrogen is fun, we still need to be careful with it. We always need to protect our _________earseyesnosemouth by wearing goggles and our _________feetearseyeshands by wearing gloves. After all, we wouldn't want to freeze and shatter like a flower!